1. Field of Invention
The present invention relates to a gene transformation method. More particularly, the present invention relates to a fast method of transforming competent cells.
2. Description of Related Art
The host cells after preliminary treatment to be more permeable to DNA molecules are called competent cells, and the technology of delivering DNA molecules in the surrounding medium into host cells is called transformation. Hence, producing competent cells and transforming competent cells is very important in view of recent developments of genetic engineering.
The technology described above can be retraced to Mandel, M. and Higa, A. (J. Mol. Biol. 53:159–162), who published a chemical transformation method using CaCl2. After 30-year-improvement, the time needed for transformation is still 1.5–3.0 hours because the host cells are injured by the chemical treatment. The injured host cells require a recovering step. In the recovering step, the host cells are cultured in a nutrient medium to allow the injured host cells to recover their physiological function and drug resistance. Then the host cells are plated on a selective medium to screen the successfully transformed host cells. Otherwise, the transformation efficiency would decrease by several times. Recently, a fast transformation method called electroporation has been developed. Although the electroporations can deliver DNA molecules into the E. coli host cells by transient current, the host cells after the transient current treatment still need an hour of recovery to obtain a higher transformation efficiency (Dower et. al., 1988 Nucleic Acids Res. 16: 6127–6145). In 1988, Golub E. I. (Nucleic Acids Res. 16: 1641) also published a method of one-minute transformation. Although a recovering step is performed, the transformation efficiency is only 104–105 colonies/μg plasmid DNA.